Method of defoliating plants

ABSTRACT

ORGANOMERCURY COMPOUNDS HAVING THE FORMULA:   R-HG-X-C(=X)-N(-R&#39;&#39;)-R&#34;   WHEREIN R IS PHENYL OR AN ALKYL-SUBSTITUTED PHENYL GROUP HAVING UP TO 12 CARBON ATOMS, R&#39;&#39; AND R&#34; ARE ALKYL GROUPS HAVING UP TO SIX CARBON ATOMS, AND X IS SULFUR WHICH POSSESS HERBITOXIC PROPERTIES. THEREFORE, FORMULATIONS CONTAINING SUCH COMPOUNDS ARE USEFUL IN CONTROLLING UNDESIRABLE VEGETATION OR IN PLANT DEFOLIATION WITHOUT KILLING THE PLANT ITSELF.

United States Patent O 3,561,946 METHOD OF DEFOLIATING PLANTS Henry G.Braxton, Jr., Franklin Village, Mich, and Evelyn J. Lajiness, Caledonia,Wis., assignors to Ethyl Corporation, New York, N.Y., a corporation ofVirginia N Drawing. Filed Oct. 31, 1968, Ser. No. 772,403

Int. Cl. A01n 9/00 US. C]. 71-70 2 Claims BACKGROUND OF THE INVENTIONThis invention relates to the control of undesirable vegetation ingeneral. More specifically, it pertains to the partial or totalmodification of the growth of plants, including defoliation and thecomplete suppression or eradication of plants. Many of the compoundsemployed in this invention and a process for their preparation have beenreported in the literature; Robert Levy et al., French Pat. 1,072,312;Chemical Abstracts, 53, 6157.

SUMMARY OF THE INVENTION The instant invention is directed tocontrolling undesirable vegetation by a method which comprisescontacting the vegetation with a herbitoxic amount of an organomercurycompound. The herbitoxic compositions of this invention may be in theform of a solution, an emulsifiable oil, a wettable powder, dust,granules, or aerosol. Depending on the specific type of the formulation,there may additionally be present a surfactant, a carrier, or anadjuvant.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The novel herbitoxiccompositions of this invention contain as an active ingredient onorganomercury compound having the formula:

wherein R is selected from alkyl, cycloalkyl, aryl, alkaryl, and aralkylgroups having up to about 12 carbon atoms, R and R" are alkyl groupshaving up to six carbon atoms, and X is oxygen or sulfur.

Examples of alkyl groups which may be present in the "ice above generalformula are methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl,sec-butyl, tert-butyl, n-amyl, and the various positional isomersthereof as, for example, l-methylbutyl, Z-methylbutyl, 3-methylbutyl,1,1-dimethylpropyl, and the like, and likewise the correspondingstraightand branched-chain isomers of hexyl, heptyl, octyl, nonyl,decyl, undecyl, and dodecyl.

Examples of aryl groups which may be present in the above formula arephenyl and naphthyl groups. Alkaryl groups Which may also be present aretolyl, 2,3-xylyl, 2-4- xylyl, 2,5-xylyl, 2,6-xy1yl, 3,4-xylyl,3,5-xylyl, o, m, and p-curnenyls, mesityl, o, m, and p-ethylphenyl,Z-methylnaphthyl, 3-methylnaphthyl, 4-methylnaphthyl, S-methylnaphthyl,6-methylnaphthyl, 7-methylnaphthyl, S-methylnaphthyl, l-ethylnaphthyl,the various positional isomers of these naphthyl radicals, and the like.Some of the examples of aralkyl groups are benzyl, phenylethyl,a-phenylpropyl, ,B-phenylpropyl, a and S-phenylisopropyl radicals, a andp-phenylbutyl radicals, and the like.

Cycloalkyl groups which may be present in the above formula areexemplified by cyclopropyl, cyclobutyl, cycloamyl, cyclohexyl,cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, cycloundecyl,cyclododecyl, and the like, or alkyl derivatives of said cycloalkylgroups such as a cyclobutylpropyl, [3 cyclobutylpropyl, and similarhigher derivatives.

In the preferred class of compounds, R is phenyl or an alkyl-substitutedphenyl having up to 12 carbon atoms, R and R" are alkyl groups having upto six carbon atoms, and X is sulfur.

Illustrative but non-limiting examples of typical active ingredients ofthis invention are listed below.

( 1) Phenylmercury diethyldithiocarbamate (2) Phenylmercurydiisopropyldithiocarbamate (3) Phenylmercury di-n-hexyldithiocarbamate(4) Phenylmercury n-butylmethyldithiocarbamate (5 O-(2,3-xylylmercury)dimethylthiocarbamate 6 S-[ (p-isopropylphenyl) mercury]ethylmethylthiocarbamate (7) (2,4,5-triethylphenyl) mercurydiethyldithiocarbamate (8) 3,5 -dipropylphenyl) mercurydimethyldithiocarbamate (9) (p-Ch1orophenyl)mercury di-n-propylcarbamate(10) (4-bromo-3,S-diethylphenyl) mercury dimethylcarbamate (1 1) S-[(pentamethylphenyl)mercury] isobutylmethylthiocarbamate (12)Methylmercury dimethyldithiocarbamate (l3) S-(isobutylmercury)dibutylthiocarbamate (14) O-(n-octylmercury) n-hexylmethylthiocarbamate(15) n-Dodecylmercury dimethyldithiocarbamate 16) S-(cyclopentylmercury)di-n-propylthiocarbamate (17) Cyclohexylmercury diethylcarbamate (18)(4-amino-n-butyl)mercury dimethyldithiocarbamate 19) 4-bromo-n-butyl)mercury ethylmethylcarbamate (20) S- 3 ,5 -dichloro-4-nitrophenyl)mercury] dimethylthiocarbamate (21) (4-amino-2,6-xylyl)mercurydiethyldithiocarbamate (22) (4-ethylcyclohexyl)mercurydimethyldithiocarbamate.

The above groups which may be present in the general formula may containvarious substituents such as halogens, hydroxy, amino, nitro, cyano, andthe like. Illustrative examples of groups having such substituents arechloromethyl, 2-bromobutyl, 1 iodo 2-propenyl, chlorophenyl,4-chlorotolyl, 1 phenyl 2-chloropropyl, fiuorocyclohexyl,3-hydroxypropyl, l-hydroxy-S-pentenyl, hydroxyphenyl, Zhydroxytolyl, lphenyl 3-hydroxyphentyl, hydroxycyclopentyl, 2-nitrobutyl, nitrophenyl,2 nitrotolyl, l-phenyl-4-nitrohexyl, nitrocyclobutyl, Z-aminobutyl,3-aminobutenyl-l, aminophenyl, 2-nitro-4-aminophenyl,2-chloro-3-nitrophenyl, 1 hydroxy 3-bromohexyl, and the like.

The class of compounds represented by the above general formula may beprepared by various methods available in the art. For the purpose ofthis invention, it is immaterial what specific method of preparation isemployed since our invention is primarily concerned with the unobvioususe of said class of compounds as herbitoxic materials. One method ofpreparing the active compounds of this invention is reported by RobertLevy et al., supra.

In a preferred embodiment, the compositions of this invention contain anactive ingredient (a compound of the type formulated and enumeratedabove and exemplifled below) and a surfactant as a dispersant therefor.In a more preferred embodiment, the herbitoxic compositions contain aninert carrier as well as a surfactant and active ingredient. Typicalsurfactants and carriers employed in this invention are discussed below.

The methods provided by this invention for treating undesirablevegetation comprise contacting living plant tissue with one or more ofthe active ingredients described and enumerated above and exemplifiedbelow. In a more preferred embodiment, undesirable vegetation is treatedwith a composition comprising one or more active ingredient, asurfactant as a dispersant therefor, and an inert carrier.

The sufactants or conditioning agents employed .in the instant inventionextend the active ingredient and promote its intimate contact with thevegetation to which it is applied. They also aid in the adaptation ofthe active ingredients for use in conventional application equipment. Ingeneral, from 0.1 to percent by weight of a surfactant is employed inthe compositions of this invention; however, greater and smaller amountscan be used, if desired.

Typical examples of surfactants which are suitable for use in thisinvention are soaps, saponins, gelatin, casein, flour, sulfite lye,synthetic cationic, anionic, and nonionic surfactants, and the like.Detailed lists of such agents are set forth by J. W. McCutcheon in Soapand Chemical Specialities, December 1957; January, February, March, andApril 1958; and in Detergent and Emulsifiers Up to Date-1960, John W.McCutcheon, Inc., 475 Fifth Avenue, New York, NY. A further discussionof surface active wetting agents is set forth by D. E. H. Frear inChemistry of Insecticides, Fungicides and Herbicides, 277-287, publishedby D. Van Nostrand Company, Inc. (1948).

The materials commonly known as carriers comprise another type ofingredient which is preferably employed in the compositions of thisinvention. The purpose of a carrier is to extend and facilitate theapplication of the active ingredient to the vegetation upon which it isapplied. In general, carriers may be of two types; viz, solids andliquids. Liquid carriers include well-known liquids such as water andvarious organic formulations. Typical liquid organic carriers arepetroleum fractions such as kerosene and diesel fuel, aromatics such asbenzene and toluene, ketones such as acetone and methylethylketone,esters such as amyl acetate, octyl acetate, and the like.

Typical solid carriers are inert solid extenders of mineral origin suchas fullers earth, kaolin, bentonite, China clay, various magnesiumsilicates, gypsum, pumice, mica, talc, attapulgite clay, and the like.Inert extenders of vegetable origin, such as soy bean flour, tobaccoflour, ground walnut shells, ground pecan shells, and the like can alsobe employed.

The herbicidal compositions of the present invention can alsobeneficially contain other adjuvants. Examples of such further adjuvantsare corrosion inhibitors, perfumes, dyes, odor-masking agents andstabilizers. In addition, other herbicidal, fungicidal, or insecticidalagents might be mixed with the herbicidal compositions of this inventionin order to obtain enhanced or. dual effects from the application of theresultant composition.

One formulation for applying the active compounds of this invention toundesirable plants is a solution or suspension of the active compound ina suitable aqueous or organic medium. The organic medium may be avolatile solvent or it may be a higher boiling solvent such as kerosene.

When using a solution or suspension formulation, a preferred activeingredient concentration range is from about 0.5 to 100 parts by weightactive ingredient per 250 parts by weight of formulation, although moreor less can be used. A more preferred concentration range is from about1 to 50 parts by weight active ingredient per 250 parts of formulation.A most preferred concentration I range is from about 1 to 10 parts byweight active ingredient per 250 parts of formulation.

Emulsifiable oil formulations which are solutions or suspensions of theactive compound in water-immiscible solvents together with a surfaceactive agent may also be used. In these formulations thewater-immiscible solvent is the carrier. Suitable water-immisciblesolvents for the active compound of this invention are hydrocarbons,such as kerosene, or xylene, and water-insoluble ethers such as dibutylCarbitol and dibutyl Cellosolve, esters such as amyl acetate and octylacetate, and ketones such as methyl ethyl ketone or dioctyl ketone. Thesolvent concentration may be from 10 to 50 to about 70 weight percent.The surfactant may be employed in a concentration from 0.5 to about 15weight percent.

A preferred active ingredient concentration of the emulsifiable oilformulations of the present invention is from about 10 to about 90weight percent. A more preferred active ingredient concentration inthese formulations is from about 20 to about 75 weight percent. A mostpreferred active ingredient concentration in the emulsifiable oilformulations of this invention is from about 25 to about 50 weightpercent.

The compositions of this invention may be formulated in the form ofwettable powders. These are water dispersible compositions whichcontain, in addition to the active compound, an inert solid extender andone or more surfactants which perform the functions previously set out.The preferred inert solid extenders used in this invention are ofmineral origin, such as fullers earth, kaolin, bentonite, China clay,and the like.

A preferred active ingredient concentration of the wettable powderformulations of this invention is from about 10 to about 90 weightpercent. A more preferred active ingredient concentration is from about20 to about weight percent, and a most preferred active ingredientconcentration in the wettable powder formulations of this invention isfrom about 50 to about 80 weight percent. The surfactant concentrationmay be from 0.5 to about 15 weight percent and preferably from 1 toabout 5 weight percent. An inert carrier may be used in the amount from10 to weight percent and more preferably from 10 to 5 0 weight percent.

Dusts are powder formulations which are intended for application in thedry form. The dust should be free flowing and have a high density. Dustformulations can contain the active compounds, an inert extender, asurfactant, and may also contain a wetting agent and a grinding aid.

A preferred active ingredient concentration employed in the dustcompositions of this invention is from about 0.1 to about 25 weightpercent, and more preferably, from about 1 to about 10 weight percent.The surfactant concentration may be from about 0.01 to about 5 weightpercent, and more preferably, from about 0.5 to about 1 weight percent.The balance of the dust compositions of this invention comprise inertfree flowing dust and any other adjuvants that might be desired, such ascorrosion inhibitors, anti-foam agents, dyes, and the like.

Granule formulations may also be employed. Granules are compositions ofmacroscopic dimension containing the activev ingredient, generally asurface active agent, and a carrier. Suitable carriers for granuleformulations are clays, pyrophyllite and vermiculite.

A preferred active ingredient concentration of the granular formulationsof this invention is from about 1 to about 50 weight percent, and morepreferably, from about 5 to about 30 weight percent. A preferredsurfactant concentration employed in the granular formulations is fromabout 0.01 to about weight percent, and a more preferred is from about0.1 to about 1 weight percent. The balance of the granular formulationsis preferably made up of about to 30 mesh particulate inert mineralcarrier.

The compounds of this invention are also effective when formulated inaerosol formulations. In these formulations, the active compounds aredissolved in an extremely volatile solvent known in the art for thispurpose and maintained under pressure in a confined space.

The active ingredients described in this invention are also useful incolloidal formulations. A colloidal formulation is prepared by passing amixture of the active ingredient, a hydrocarbon solvent, and a largeamount of water through a colloid mill until homogenation of the oil andwater is achieved.

The above-discussed formulations and additives are disclosed in greaterdetail in a copending application Ser. No. 530,778, filed Mar. 1,1966.

The compounds used in the following Examples 1 to 7 will have thedesignations given below:

(A) Phenylmercury dimethyldithiocarbamate (B) o-Tolylmercurydimethyldithiocarbamate (C) O-(phenylmercury) diethylthiocarbamate (D)(2,4-diethylphenyl) mercury diethylcarbamate (E) S-(phenylrnercury)dimethylthiocarbamate (F) Ethylmercury dimethyldithiocarbamate (G)O-phenethyl dibutylthiocarbamate (H) n-Hexylmercury dipropylcarbamate.

The following examples serve to illustrate the herbitoxic formulationsof this invention. All percentages are by weight.

Example 1 Percent Compound A 50 Bentonite. 49 Sodium alkyl benzenesulfonate 1 The above wettable powder is prepared by blending the drycomponents and grinding until substantially all of the particles aresmaller than 50 microns.

For application, the above wettable powder is dispersed in Water inquantities equivalent to one pound of active ingredient per 30 gallonsof Water. The dispersion so formed is conveniently applied by the use ofany of the various commercial sprayers.

Example 2 Percent Compound B 90 Sodium alkyl naphthalene sulfonate 0.5Kaolin 9.5

The above wettable powder is prepared in the same manner as inExample 1. For application, it is dispersed in water at a rateequivalent to 10 pounds of active ingredient per 30 gallons of water.

In the above example, similar formulations may be prepared containing20, 30, 40, 50, 60, 70, 80, or 90 percent Compound C and correspondinglysmaller amounts of carrier.

Example 3 Percent Compound D 10 Talc Diatomaceous silica 8 Fatty acidamides 2 The above dust is prepared by first grinding together theactive ingredients, diatomaceous silica and fatty acid amide and thenblending in the talc and thoroughly mixing.

This dust formulation can be applied using a tractor or airplane-mountedduster, at a rate of about 5 pounds of active ingredient per acre.

Example 4 Percent Compound E 25 Diesel fuel 65 Alkylaryl polyetheralcohols 10 The above emulsifiable oil is prepared by mixing thecomponents until a homogeneous solution results.

The above composition is conveniently applied by dispersing thecomposition in water at a rate equivalent to two pounds of activeingredient per 30 gallons of water. It may then be applied using anysuitable commercial sprayer.

In the above example, similar formulations are prepared containing 10,20, 30, 40, 50, 60, 70, 80, or percent Compound E and correspondinglysmaller amounts of diesel fuel.

Example 5 Percent Compound F 30 Sodium alkyl naphthalene sulfonate 515-30 mesh attapulgite 65 The above granular composition is prepared byfirst dissolving the active ingredient and surface active agent in avolatile solvent and then spraying the solution on the carrier.Following this, the granules are dried. It may then be applied to planttissue at a rate of from about 1 to 10 pounds of active ingredient peracre.

In the above example, similar formulations are prepared containing 10,40, 60, 80, and 90 percent of Compounds E and F, and correspondinglysmaller amounts of attapulgite.

Example 6 Into a cylinder rated at p.s.i.g. working pressure isintroduced 10 parts of Compound G. The cylinder is then made pressuretight except for one opening, through which is introduced a mixture of10 parts of acetone and 50 parts of dichlorodifluoromethane, from acontainer holding this material under 2000 p.s.i.g. The cylinder intowhich the ingredients have been introduced is then sealed off and shakento give a uniform solution of the active compound in the volatilesolvents. When sprayed into the atmosphere this solution will form aneffective aerosol of the active compound employed.

In the above example, similar formulations are prepared containing 10,30, 60 and 90 percent of Compound G and correspondingly smaller amountsof the solvent.

Example 7 A colloidal formulation is prepared by passing a mixture of 10parts of Compound H, 100 parts of kerosene, 1000 parts of water, and 1part of mannitan monooleate through the colloid mill until homogenationof the oil in water is achieved.

Examples 8 to 161 Compounds 122. set forth above are incorporated, oneat a time, in each of the foregoing Examples 1 through 7.

The compositions of this invention are extremely useful when employed inthe method of this invention for controlling the growth of undesirablevegetation. Not only are they phytotoxic to many undesirable plants, butthey are also useful as defoliants. The compositions of this inventionare active as plant growth regulants at rates as low as one-tenth poundof active ingredient per acre. A preferred application rate is from 1 to60 pounds of active ingredient per acre, and a most preferredapplication rate is from 5 to pounds of active ingredient per acre.Higher or lower rates can be employed, depending upon the effect thatthe particular user desires to accomplish.

The compositions of the present invention are usually contacted with theleaves and stems of growing plants in the terms broadest sense, but canbe applied to soil to obtain preemergence herbitoxic effects.

As appreciated in the art, the morphological effect obtained with theactive ingredients of this invention may be influenced by theapplication rate, ambient temperature, humidity, and the time of thelife cycle of the plant to which the compositions are applied, Theeffect usually desired of plant growth regulators is either defoliationor complete eradication of undesirable species. It is in theseparticular applications that the compositions of this invention are mostuseful. The following tests were carried out in order to demonstrate theuseful properties of the compositions of this invention.

In test procedure A, the compounds were formulated as follows. Eachcompound was weighed into a small alu-,

minum cup. The material was then washed into small beakers with about 5ml. of acetone, followed by m1. of water, giving a total volume of ml. Aquantity of this material containing 31 mg. of the test compound wasthen removed and water added to it to bring its volume to 11 ml. At thispoint, 0.5 ml. of a one weight percent solution of Triton X-155 wasadded to the test solution and its volume then raised to 15 ml. by theaddition of water. When this test solution is sprayed over an area ofone-third square yard, it approximates an application rate of gallonsper acre containing one pound of test chemical per acre.

In some experiments the test compound was merely dissolved in acetone,so that 12 ml. of acetone solution contained 31 mg. of test compound.

The spray chamber used in carrying out subsequent tests was about 36inches wide, 18 inches deep, and 26 inches high. It was made of clearplastic and the front of the chamber had sliding doors suitable forplacing plants in and removing plants from the chamber. The top of thechamber had a hole for introducing the spray.

The compounds were examined by spraying them on 14-day-old BlackValentine bean plants and in some instances on privet plants at a rateequivalent to one pound of test compound per acre.

In the following Table I, the effectiveness of the compounds of thisinvention are expressed in terms of their phytotoxicity and theirability to cause abscission (defoliation). The abscission value isexpressed in terms of the percentage drop of the total leaves on theplant (percent defoliation). At the time of spraying, the bean plantsusually have two primary leaves. However, during the 14 days the plantis observed following spraying, two more (trifoliate) leaves usuallyemerge. Dropping of the two primary leaves would be recorded as percentabscission. Dropping of all four leaves would be recorded as 100 percentabscission. Actually, dropping of the two primary leaves wouldconstitute a total drop of all leaves actually contacted with the testcompound.

Phytotoxicity is a measure of leaf damage (not to be confused with leafdroppage) and is estimated visually on a scale from 0 to 11, where 0indicates no effect and 11 indicates all leaves killed. It is possiblefor a test chemical to have a phytotoxicity rating of 11 and yet have anabscission rating of 0, which means that although all leaves werekilled, they remained on the plant.

TABLE I.ABSOISSION AND PHY'IOTOXICITY RATINGS OI PHENYLMEROURYDIMETHYLDITHIOCARBAMAIE ON BLACK VALENTINE BEANS Percent Phyto-Concentration defoliation toxicity 01 lb./acre (Water) 0 1 1.0 lb./acre(Water) 30 1 1.0 lbJacre (Acetone) 35 0 Further tests were carried outon the compounds of this invention to more fully determine theeffectiveness of such compounds. In test procedure C, the test compoundwas dissolved in acetone containing 0.5% Tween-20. The concentrationswere adjusted so that rates of 1.0 lb./acre and 0.1 lb./ acre could beapplied. Each rate was applied in duplicate to six different 7-day-oldspecies. The test plants used were Black Valentine bean, Heavenly BlueMorning-Glory, Scarlet Globe Radish, Lincoln Soybean, Clinton Oats andRice (RI. 8970). At selected time intervals, the following effects werenoted: abscission, chlorosis, contact injury, curvature, formativeeffects, galling, killing, necrosis, abnormal pigmentation, quilling,adventitious roots, and stunting. A rating system ranging from a valueof l to 4 was used for each species. When the plant appeared normal, arating of one was assigned, whereas when the plant was killed, a valueof 4 was as signed. Thus, the ratings are such that a maximum value of 4for each species may be obtained. Since there are six species and eachmay obtain a value of from one to four, the overall result will alwaysfall within the range of from 6 to 24. The latter indicates completekill of all the species. The former indicates no effect, Final readingsare obtained 10 to 14 days after application. The following Table IIshows the overall result obtained when the indicated organomercurycompounds were applied on the above-described six species.

TABLE II.SUMMARY HERBICIDAL PROPERTIES OF PHENYLMERCURYDIMETHYLDITHIOCAR- BAMATE Rating based on a Concentration: maximum of 240.1 lb./acre 10 1.0 lb./acre 18 As noted above, certain herbitoxicformulations require an organic medium or a. solvent. In addition to thesolvents and the organic medium materials listed above, alcohols andsulfoxides may also be employed. Nonlimiting examples of alcohols arel-butanol, cyclohexanol, l-octanol, l-nonanol, and the remainingpositional isomers, Q-methyl-l-nonanol, 2,8-dimethyl-5-nonanol,ldodecanol, d-dodecanol, l-tetradecanol, all positional isomers thereof,and the like. Illustrative examples of sulfoxides are dimethylsulfoxide, diethyl sulfoxide, di-npropyl sulfoxide, di-n-butylsulfoxide, dibenzyl sulfoxide, and the like.

This invention can be extended to the treatment of species of plantsother than those mentioned above, such as algae.

Having fully described the compositions of this invention and theirnovel uses, it is desired that this invention be limited only within thelawful scope of the appended claims.

We claim:

1. A method of defoliating plants which comprises contacting the plantswith a defoliating amount of a compound having the formula:

wherein R is phenyl or an alkyl-substituted phenyl group having up to 12carbon atoms, R and R" are alkyl groups having up to six carbon atoms,and X is sulfur.

2. The method of claim 1 wherein said compound is phenylmercurydimethyldithiocarbamate.

1 0 References Cited UNITED STATES PATENTS 3,442,638 5/1969 Wollensak eta1. 71-97 3,433,622 3/1969 Plonsker et a1 7170 5 3,433,618 3/1969Wollensak et a1. 7170 2,754,241 7/1956 Schwerdle 7197 2,637,677 5/1953Dinerstein 7197 LEWIS GOTTS, Primary Examiner 10 C. L. MILLS, AssistantExaminer US. Cl. X.R. 71-97

